The migration of transistor technology from planar to FINFET utilizes conformal work function layers suitable for multiple threshold voltages (Vt). The threshold voltages (Vt) tuning range is limited by the thickness variation with further scaling down of device sizes. The inventors have discovered that a dipole layer can serve to shift the work function in both PMOS and NMOS type transistors.
Accordingly, the inventors have developed improved semiconductor devices incorporating multi-threshold voltage structures and improved methods of forming such semiconductor devices.